linux-kernel - Re: [RFC][PATCH 00/15] sched: SCHED

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Date:	Tue, 29 May 2012 12:07:18 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Juri Lelli <juri.lelli@...il.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, rostedt@...dmis.org,
	oleg@...hat.com, fweisbec@...il.com, darren@...art.com,
	johan.eker@...csson.com, p.faure@...tech.ch,
	linux-kernel@...r.kernel.org, claudio@...dence.eu.com,
	michael@...rulasolutions.com, fchecconi@...il.com,
	tommaso.cucinotta@...up.it, nicola.manica@...i.unitn.it,
	luca.abeni@...tn.it, dhaval.giani@...il.com, hgu1972@...il.com,
	paulmck@...ux.vnet.ibm.com, raistlin@...ux.it,
	insop.song@...csson.com, liming.wang@...driver.com,
	jkacur@...hat.com, harald.gustafsson@...csson.com
Subject: Re: [RFC][PATCH 00/15] sched: SCHED_DEADLINE v5

On Mon, 2012-05-28 at 11:06 +0200, Juri Lelli wrote:
>   o  The only "big problem" I fear is related to the current deadline
>      inheritance mechanism. As Steven pointed out during the last review,
>      a task could force more bandwidth than was allowed if:
> 
>         - it takes a futex;
>         - it is boosted while holding it;
>         - never releases the futex;
> 
>      and this is sadly achievable since, if boosted, a task inherits top
>      waiter parameters and the enforcement mechanism is temporarily
>      disabled for it. 

/me goes read patch 12 in detail..

Wouldn't it be possible to enforce pi_se (aka. pi_task)'s bandwidth in
the dl-boosts-dl case?

Since afaict that's the only case we need to worry about. If you can
spawn FIFO/RR tasks you already loose bandwidth caps etc..


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